I read the FAQ thread about singing and playing, but it still leaves me with an unanswered question: I have a really hard time separating my strumming rythm and my singing rythm. Is there any way to cure this? All my songs sound kind of one-dimensional. Some artists can do this very well, for example my band did a cover of Smells Like Teen Spirit, and for the life of me I could not sing and play the chorus because the two rythms weren't similar enough...

Any tips or suggestions would be greatly appreciated.

Well, I have had this problem, but it's not as bad with me.... I can play something that has nothing to do with the song, like playing DragonForce or Avenged Sevenfold.... basically, you just gotta practice.. that's why I can play random stuff and sing now. just practice and get everything down so you can nail it while sleeping
Practicing the two parts separate will help, but won't fix the problem.
IMO, you need to know the song basically better than a regular guitarist would.

If you can play a song on guitar perfectly, it doesn't mean you can sing it. You need to be able to play it sort of absentmindedly, while still playing it perfectly...

...what I'm getting at is: practice.
Learn to block yourself out. If you pay attention to both you will **** yourself pretty hard. You should know both parts of the song well enough so that at any given moment you can concentrate on one while still being able to do the other without having to pay attention to it. IE if you have to solo while singing you should be able to know the singing well enough to assume that you're doing it right without having to think about it so that you can concentrate on ensuring that you're soloing right.
People writing songs that voices never shared
No one dared
Disturb the Sound of Silence